Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w=map(int,input().split())
maze=[list(input()) for i in range(h)]
distance=[[-1]*w for i in range(h)]

cnt=0
for i in maze:
  cnt+=i.count('#')

Q=[[0,0]]
distance[0][0]=1

ans=-1

while Q:
  p=Q.pop(0)
  if p[0]==h-1 and p[1]==w-1:
    ans=h*w-cnt-distance[h-1][w-1]
    break

  dx=[1,-1,0,0]
  dy=[0,0,1,-1]

  for i in range(4):
    nx=p[0]+dx[i]
    ny=p[1]+dy[i]

    if 0<=nx<h and 0<=ny<w and distance[nx][ny]==-1 and maze[nx][ny]!='#':
      Q.append([nx,ny])
      distance[nx][ny]=distance[p[0]][p[1]]+1

print(ans)